Fuel cell device and related control method

ABSTRACT

A fuel cell device and related control method are disclosed wherein a water tank  5  is disposed downstream of a fuel cell stack  1  and a hot medium flow passage  25  is formed on an outer periphery of the water tank  5  to pass antifreeze solution. During cold start-up, a three-way vale  13  is switched over to allow antifreeze solution to flow through the fuel cell stack  1  and a heat exchanger  17 , by which antifreeze solution is heated and supplied to the fuel cell stack  1  and the water tank  5  to heat these components, whereby the water tank  5  is heated to thaw frozen ice.

TECHNICAL FIELD

The present invention relates to a fuel cell device equipped with awater storage means that stores water required for a fuel cell.

BACKGROUND ART

In cases where water becomes frozen in a water tank during a cold time,to rapidly thaw such a frozen state needs for permitting water to bequickly supplied to the fuel cell.

In this respect, Japanese Application Laid-Open No. 2000-149970discloses a fuel cell device which includes a water tank to supply waterto the fuel cell, with the water tank employing a double-layer structureadapted to be heated by a heater.

DISCLOSURE OF THE INVENTION

However, although the heater of the fuel cell device is incorporated ina heat insulation material through which the water tank is heated, whenthawing ice in the water tank a poor heat conductivity results inbetween the water tank and the heater, with a resultant inability causedin efficiently heating the water tank.

Therefore, it is an object of the present invention to provide a fuelcell device and a related control method for efficiently and rapidlythawing frozen ice in a water tank.

To achieve the object, a first aspect of the present invention is a fuelcell device comprising a fuel cell cooled by antifreeze solution, anantifreeze circulation flow passage to allow the antifreeze solution tobe circulated, an antifreeze heater disposed in a midway of theantifreeze circulation flow passage to heat the antifreeze solution, awater storage unit that stores water to be supplied to the fuel cell,and a hot medium flow passage disposed in a water contact section of thewater storage unit to allow the antifreeze solution, heated by theantifreeze heater, to flow.

A second aspect of the present invention is a method of controlling afuel cell device, the method comprising preparing a fuel cell, preparinga water storage unit, to store water to be supplied to the fuel cell,that has a hot medium flow passage, circulating antifreeze solution tothe fuel cell and the hot medium flow passage through an antifreezecirculation flow passage, and heating the antifreeze solution flowingthrough the antifreeze circulation flow passage for thereby heating thewater in the water storage unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system structural view of a fuel cell device of a firstembodiment according to the present invention.

FIG. 2 is a perspective view of a water tank of the first embodiment

FIG. 3 is a cross sectional view of the water tank of the firstembodirnent.

FIG. 4 is a cross sectional view of a water tank showing a secondembodiment.

FIG. 5 is a perspective view of a water tank showing a third embodiment.

FIG. 6 is a cross sectional view, as viewed in a right direction in FIG.5, illustrating a skeletal form of an internal structure of the watertank of the third embodiment.

FIG. 7 is a perspective view illustrating an internal structure of awater tank showing a fourth embodiment.

FIG. 8 is a perspective view illustrating an external structure of awater tank showing a fifth embodiment.

FIG. 9 is a front view illustrating an external structure of a watertank showing a sixth embodiment.

FIG. 10 is a right side view of the water tank shown in FIG. 9.

FIG. 11 is a system structural view of a fuel cell device of a seventhembodiment according to the present invention.

FIG. 12 is a flowchart illustrating a basic sequence of operations, tobe performed during switch-over of antifreeze solution, of the seventhembodiment.

FIG. 13 is a system structural view of a fuel cell device showing aneighth embodiment according to the present invention.

FIG. 14 is a flowchart illustrating a basic sequence of operations, tobe performed during switch-over of antifreeze solution, of the eighthembodiment.

FIG. 15 is a system structural view of a fuel cell device of a ninthembodiment according to the present invention.

FIG. 16 is a flowchart illustrating a basic sequence of operations, tobe performed during switch-over of antifreeze solution, of the ninthembodiment.

FIG. 17 is a flowchart, illustrating how a switch-over flag isdetermined during switch-over of antifreeze solution, that shows a tenthembodiment according to the present invention.

FIG. 18 is a system structural view of a fuel cell device showing aneleventh embodiment according to the present invention.

FIG. 19 is a flowchart illustrating a basic sequence of operations ofthe eleventh embodiment.

FIG. 20 is a cross sectional view of a water tank, in a fuel cell deviceof a twelfth embodiment according to the present invention, whereinantifreeze solution is introduced into a hot medium flow passage.

FIG. 21 is a cross sectional view of the water tank, in the fuel celldevice of the twelfth embodiment according to the present invention,wherein air is admitted to the hot medium flow passage.

FIG. 22 is a perspective view of a heat insulation member to beaccommodated in the hot medium flow passage of the twelfth embodiment.

FIG. 23 is a cross sectional view of a water tank, in a fuel cell deviceof a thirteenth embodiment according to the present invention, whereinantifreeze solution is admitted to a hot medium flow passage.

FIG. 24 is a cross sectional view of the water tank, in the fuel celldevice of the thirteenth embodiment according to the present invention,wherein air is admitted to the hot medium flow passage.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present invention aredescribed with reference to the attached drawings.

FIG. 1 is a system structural view of a fuel cell device illustrating afirst embodiment according to the present invention. The fuel celldevice, which is referred to here, is intended to be installed on avehicle and includes an antifreeze circulation passage 3, thatcirculates antifreeze solution to cool a fuel cell stack 1, and a watertank 5 that serves as water storage means for storing water, to humidifyair containing oxygen serving as oxidant to be supplied to the fuel cellstack 1 described above, or water to be mixed as steam with methanol toproduce hydrogen in a structure equipped with a methanol reformer.

Water in the water tank 5 is drawn by a pump 7 and supplied to the fuelcell stack 1 for the purpose of humidifying the same as set forth above.Water expelled from the fuel cell stack 1 is returned to the water tank5 through a return flow passage 9.

Antifreeze solution, whose temperature is increased after having cooledthe fuel cell stack 1 in which heat builds up, is cooled in a radiator11 and fed through a three-way valve 13 to the fuel cell stack 1.

Further, the antifreeze circulation passage 3 includes a heat-exchangebypass flow passage 15, that bypasses the radiator 11 and has one endconnected to the three-way valve 13, in which a heat exchanger 17 islocated which serves as an antifreeze heating means. The heat exchanger17 is supplied with combustion gas generated in a hydrogen combustor 19to heat antifreeze solution.

The hydrogen combustor 19 is supplied with hydrogen and air, which arecombusted. The hydrogen results from hydrogen obtained in the methanolreformer stated above or hydrogen stored in a hydrogen tank, orexcessive hydrogen expelled from the fuel cell stack 1. Also, use ismade for air that comes from air, diverged from an air flow passage, tobe supplied to the fuel cell stack 1.

As shown in FIG. 2 and FIG. 3, the water tank 5 takes the form of adouble-layer structure comprised of an inside tank component 21, whichserves as a water contact section, and an outside tank component 23,with a spacing defined between the inside tank component 21 and theoutside tank component 23 to form a hot medium flow passage 25 to allowthe above-described antifreeze solution to flow.

Disposed in an upper area of the water tank 5 at right side thereof inthe figure is an antifreeze solution inlet 27 that allows antifreezesolution to be admitted to the hot medium flow passage 25 from theantifreeze circulation passage 3, and disposed in a lower area of thewater tank 5 at left side thereof in the figure is an antifreezesolution outlet 29 that allows antifreeze solution prevailing in the hotmedium flow passage 25 to be discharged into the antifreeze circulationpassage 3.

The water tank 5 has a top portion that is formed with an openingportion, to which a lid 31 is mounted to cover the same. Connected to alower end of the water pump 7 is a water suction conduit 33 that extendsthrough the lid 31 and its distal end (lower end) reaches the vicinityof a bottom portion of the water tank 5 while carrying a strainer 35.Also, the return flow passage 9 extends through the lid 31 and has itsdistal end exposed to an inside of the water tank 5. Additionally,mounted on the water tank 5 are air bleeder 37 that suppresses increasein an internal pressure, a water level meter 39 that measures a watervolume in the water tank 5, and a water temperature gauge 41 that servesas a temperature detection means for measuring the temperature of waterin the water tank 5.

Also, in FIG. 2, the water pump 7 and air bleeder 37 mounted on thewater tank 5 are omitted.

Now, operation of the fuel cell device of the presently filed embodimentis described.

During a normal traveling mode of a vehicle, the three-way valve 13remains in a state to allow flow paths 13 a, 13 b to communicate oneanother and, hence, antifreeze solution flows through the fuel cellstack 1 and the radiator 11 so as to circulate through the antifreezecirculation passage 3 in a direction as shown by an arrow A. When thistakes place, antifreeze solution absorbs heat from the fuel cell stack1, whose temperature is raised during operation, and dissipates the samein the radiator 11, thereby adjusting the temperature of (cooling) thefuel cell stack 1.

During a cold start-up mode, the three-way valve 13 remains in a stateto allow flow paths 13 c, 13 b to communicate one another and, hence,antifreeze solution flows through the fuel cell stack 1 and the heatexchanger 17 so as to circulate through the antifreeze circulationpassage 3, involving the heat exchange bypass flow passage 15, in adirection as shown by an arrow B.

When this takes place, the hydrogen combustor 19 is supplied withhydrogen for combustion, with resulting combustion gas being used asheating medium of the heat exchanger 17 by which antifreeze solution isheated. Heated antifreeze solution then passes through the fuel cellstack 1 to heat the same whereupon heated antifreeze solution flowsthrough the antifreeze solution inlet 27 of the water tank 5 to the hotmedium flow passage 25.

Antifreeze solution, admitted to the hot medium flow passage 25, thawsice, that is formed when water is condensed in the water tank 5, and,thereafter, flows out from the antifreeze solution outlet 29 to theantifreeze circulation passage 3 to be returned to the heat exchanger17. As far as hydrogen is supplied to the hydrogen combustor 19,antifreeze solution is heated, with resulting heat medium heating thefuel cell stack 1 and the water tank 5.

Thawed water in the water tank 5 is drawn by the water pump 7 and usedfor heating the fuel cell stack 1. Also, combustion gas expelled fromthe heat exchanger 17 is exhausted to the outside of the vehicle.

Thus, according to the first embodiment set forth above, a heat valueresulted in antifreeze solution heats ice (water) in the water tank 5via the inside water tank component 21 which is held in contact withwater inside the water tank 5, thereby enabling a thawing phase to beefficiently completed in a rapid fashion.

Further, due to the presence of the antifreeze solution inlet 27 locatedin the water tank 5 at an area higher than the antifreeze solutionoutlet 29, heat exchange takes place between water (ice), prevailing inan upper portion where temperature is relatively lower than that of alower portion due to the existence of ice that is floating because ofthe small specific gravity during the thawing phase, and antifreezesolution prevailing closer to the antifreeze solution inlet 27 (with nodrop in temperature) and, therefore, a temperature difference betweentwo media relatively increases, resulting in a capability of efficientlyand rapidly achieving the thawing phase.

Additionally, in such case, since the water tank 5 is heated usingantifreeze solution, that is heated by the heat exchanger 17, forheating the fuel cell stack 1, no separate heating means, such as aheater, specific for heating the water tank 5 is required.

FIG. 4 is a cross sectional view of a water tank 5A illustrating asecond embodiment of the present invention. Also, here, the samecomponent parts as those of the first embodiment bear like referencenumerals and only differing portions are described.

In the presently filed embodiment, a suction conduit heating section 43through which antifreeze solution flows is located around a periphery ofthe water suction conduit 33 of the water pump 7. The suction conduitheating section 43 takes the form of a cylindrical shape and is soconfigured as to extend from an upper end portion of the water suctionconduit 33 toward a substantially central area thereof in a verticaldirection, with one end of the antifreeze solution inlet 27 beingconnected to the vicinity of a lower end of the suction conduit heatingsection 43. The other end of the antifreeze solution inlet 27 extendsthrough the water tank 5A to be taken out to the outside of the watertank 5 and is connected to the antifreeze circulation passage 3 as shownin FIG. 1 as set forth above.

Further, here, the lid 31 is internally formed with a hot medium flowpassage 31 a, through which antifreeze solution flows, that is incommunication with the hot medium flow passage 25 and the suctionconduit heating section 43, respectively. That is, antifreeze solutionflowing through the antifreeze circulation passage 3 shown in FIG. 1flows to the suction conduit heating section 43 from the antifreezesolution inlet 27 and, subsequently, flows into the hot medium flowpassage 25 through the hot medium flow passage 31 a to reach theantifreeze solution outlet 29. Consequently, the lid 31 is placed on theupper opening of the water tank 5A to seal the upper opening watertight.Other structure is identical to that of the first embodiment.

According to the structure of the presently filed embodiment, heatedantifreeze solution flows from the antifreeze solution inlet 27 into thesuction conduit heating section 43 to heat water in the water suctionconduit 33 and, thereafter, flows through the hot medium flow passage 25between the inside water tank component 21 and the outer water tankcomponent 23, thereby heating ice (water). When this takes place, sinceit is possible to heat water being drawn by the water pump 7, it ispossible to prevent water from being frozen again in the water pump 7where a high probability exists in the cold temperature condition below0 C.

FIG. 5 is a perspective view of a water tank 5B showing a thirdembodiment of the present invention. FIG. 6 is a cross sectional view ofthe water tank as viewed in a right direction in FIG. 5 to show anoutline of an internal structure of such a water tank 5B. Also, althoughthe water tank 5B takes the form of a double-layer structure equippedwith the inside tank component 21 and the outside tank component 23 likein the first embodiment shown in FIG. 1, the component elements, such asthe lid 31, the water pump 7 and the air bleeder 37, which are mountedin the water tank 5 are omitted in a simplified form, and the samecomponent parts as those of the first embodiment bear the same referencenumerals to describe only differing portions.

In the presently filed embodiment, a spiral shaped antifreezerectification plate 45 is disposed in the hot medium flow passage 25between the inside tank component 21 and the outer water tank component23 to guide antifreeze solution to the antifreeze solution outlet 29through the antifreeze solution inlet 27. The antifreeze rectificationplate 45 has an inner periphery fixedly secured to an outer peripheralsurface of the inside water tank component 21. Meanwhile, in order foran edge portion of an outer peripheral side of the antifreezerectification plate 45 to have less heat transfer with the outside ofthe water tank 5B, the edge portion is out of contact with the innerperiphery of the outside tank component 23 (see FIG. 6).

With the structure of the presently filed embodiment, antifreezesolution introduced from the antifreeze solution inlet 27 into the hotmedium flow passage 25 flows along the antifreeze rectification plate 45and flows out from the antifreeze solution outlet 29.

Accordingly, in such case, antifreeze solution substantially uniformlyflows throughout an entire area of the hot medium flow passage 25without depending upon the flow rate and temperature, enabling efficientheat exchange to take place.

FIG. 7 is a perspective view illustrating an internal structure of awater tank 5C of a fourth embodiment of the present invention. Also,here, the same component elements as those of the first embodiment setforth above bear the like reference numerals and differing portions aremainly described. Also, in FIG. 7, the component elements, such as thelid 31, the water pump 7 and the air bleeder 37, mounted in the watertank 5 are omitted.

In the presently filed embodiment, the water tank 5C has no double-layerstructure, and a plurality of annular conduits 47 (conduit components 47a, 47 b, 47 c, . . . , 47 g, 47 h), forming a hot medium flow passagethat is disposed in an annular configuration along an inner wall of thewater tank 5C, are disposed in a stacked structure with a given distanceprevailing in a vertical direction in the figure. Then, the antifreezesolution inlet 27 is connected to the uppermost annular conduit 47 a,and the antifreeze solution outlet 29 is connected to the lowermostannular conduit 47 h.

Here, the uppermost annular conduit 47 a and an adjacent lower annularconduit 47 b are connected at one side (on a left side wall in FIG. 7)of the water tank 5 opposite to the antifreeze solution inlet 27 and theantifreeze solution outlet 29 by means of a connecting conduit 49. Inaddition, the third and fourth annular conduits 47 c, 47 d are mutuallyconnected by means of a connecting conduit 51, the fifth and sixthannular conduits 47 e, 47 f are mutually connected by means of aconnecting conduit 53, and the seventh and eight annular conduits 47 g,47 h are mutually connected by means of a connecting conduit 55,respectively, at the one side of the water tank 5 opposite to theantifreeze solution inlet 27 and the antifreeze solution outlet 29.

Further, the second and third annular conduits 47 b, 47 c, the fourthand fifth annular conduits 47 d, 47 e and the sixth and seventh annularconduits 47 f, 47 g are mutually connected by means of connectingconduits 57, 59, 61, respectively, on the other side of the water tank 5at which the antifreeze solution inlet 27 and the antifreeze solutionoutlet 29 are located.

Thus, antifreeze solution, that enters from the antifreeze solutioninlet 25 into the uppermost annular conduit 47 a, flows through theannular conduit 47 a leftward in the figure to enter from the connectingconduit 49 into the lower annular conduit 47 b, from which antifreezesolution then flows rightward in the figure to enter from the connectingconduit 57 into the lower annular conduit 47 c.

In such a way, antifreeze solution sequentially flows through therespective annular conduits 47, that are stacked up and down, and flowsin a downward direction whereupon it finally flows out from theantifreeze solution outlet 29, that is connected to the lower mostannular conduit 47 h, to the outside. For this reason, with thepresently filed embodiment, uniform flow of antifreeze solution can beobtained without depending upon the flow rate or the temperature thereofand a surface area between water (ice), forming a body to be heated, andthe annular conduit 47 can be increased, enabling efficientheat-exchange.

Also, the annular conduit 47 of the presently filed embodiment does notneed to be disposed in a substantially entire area of the water tank 5Calong a vertical direction thereof, but may be disposed only in a lowerarea where water is received.

Further, in place of the annular conduits 47, a spiral shaped conduitmay be provided which takes the form of a spiral configuration extendingfrom an upper portion to a lower portion in the figure. In such case, noconnecting conduits 49 to 61 are required. The presence of the flowpassage formed in the spiral configuration to pass antifreeze solutionprovides a more simplified structure to be easily manufactured than thatof the annular type, resulting in reduction cost.

FIG. 8 is a perspective view illustrating an external structure of awater tank 5D of a fifth embodiment of the present invention. Also,here, the same component parts as those of the first embodiment bear thesame reference numerals and reference is mainly made in only differingportions. Further, in FIG. 8, the component elements, such as the waterpump 7 and the air bleeder 37, that are mounted in the water tank 5 areomitted.

The presently filed embodiment is configured to have a water tank 5Dthat has a side wall by which a hot medium flow passage is formed. Thehot medium flow passage in this case is comprised of a plurality ofannular conduits 47 (conduit components 47 a, 47 b, 47 c, . . . 47 g, 47h) that have the same structures as those shown in FIG. 7, with mutuallyadjacent portions being mutually joined by brazing to be stacked insealed watertight state.

Further, communication ports 49 a to 61 a, that allow the adjacentannular conduits 47 to mutually communicate one another, are formed inthe annular conduits, respectively, at positions corresponding to theconnecting conduits 49 to 61 of the embodiment shown in FIG. 7.

Accordingly, in the presently filed embodiment, antifreeze solutionsequentially flows downward through the respective annular conduits 47stacked up and down and flows out to the outside from the antifreezesolution outlet connected to the lowermost annular conduit 47 h.

Furthermore, a lower portion of the lowermost annular conduit 47 h isclosed by brazing a tank bottom plate 63. Meanwhile, a lid 31 is joinedto or detachably placed on an upper portion of the uppermost annularconduit 47 a.

Consequently, in the presently filed embodiment, flow of antifreezesolution can be uniformed while constructing the side wall of the watertank 5D enables production in light weight.

Also, the annular conduits 47 in the fifth embodiment set forth abovedoes not need to be disposed in the substantially entire area of thewater tank 5D along the vertical direction thereof like in the fourthembodiment and may be disposed only in the lower area where water isreceived.

FIG. 9 is a front view illustrating an external structure of a watertank 5D showing a sixth embodiment of the present invention, and FIG. 10is a right side view of FIG. 9. Also, here, the same component elementsas those of the first embodiment bear the like reference numerals andreference is mainly made only in differing portions. Further, in FIGS. 9and 10, the component elements, such as the water pump 7 and the airbleeder 37, that are mounted in the water tank 5 are omitted.

In the presently filed embodiment, in place of the annular conduits 47of the fifth embodiment shown in FIG. 8 set forth above, a spiral shapedconduit 65 is provided which serves as a hot medium flow passage formedin a spiral configuration extending from an upper portion to a lowerportion in the figure. In such case, mutually adjacent portions facingup and down of the spiral-shaped conduit 65 is sealed watertight, and nocommunication ports 49 a to 61 a shown in FIG. 8 are required.

Disposed between the uppermost end of the spiral shaped conduit 65 andthe lid 31 is a lid joint member 67, for jointing or detachably mountingthe lid 31, that is joined in a watertight condition. Also, disposedbetween the lower most end of the spiral shaped conduit 65 and the tankbottom plate 63 is a lid joint member 69, for jointing or detachablymounting the tank bottom plate 63, that is joined in a watertightcondition. The antifreeze solution inlet 27 is connected to theuppermost end of the spiral shaped conduit 65, and the antifreezesolution outlet 29 is connected to the lowermost end of the spiralshaped conduit 65.

Accordingly, in the presently filed embodiment, the presence of the hotmedium flow passage formed in the spiral shape allows a structure to befurther simplified to provide an ease of manufacturing than that of thecase configured in the annular shape shown in FIG. 8, achievingreduction in cost.

FIG. 11 is a system structural view of a fuel cell device illustrating aseventh embodiment of the present invention. Also, here, the samecomponent elements as those of the first embodiment bear the samereference numerals and reference is mainly made only in differingportions.

In the presently filed embodiment, antifreeze solution is dischargedfrom the hot medium flow passage 25 of the water tank 5, and exhaustedantifreeze solution is replaced with air that flows through the hotmedium flow passage 25.

As a system structure, in addition to the structure shown in FIG. 1 setforth above, three-way valves 71, 73 serving as hot medium switch-overmeans are disposed in the antifreeze solution flow passage 3 at upstreamand downstream sides of the hot medium flow passage 25 of the water tank5, respectively.

Connected to the three-way valve 71 upstream of the water tank 5 is anair flow supply passage 75 through which air branched off from a flowpath of air stream to be supplied to the fuel cell stack 1 is admitted,and connected to the three-way valve 73 downstream of the water tank 5is one end of an antifreeze solution discharge flow passage 77. Theother end of the antifreeze solution discharge flow passage 77 is openedto an antifreeze drain tank 79 that serves as an antifreeze recoverymeans to allow antifreeze solution, expelled from the antifreeze draintank 79, to be returned thereto.

Next, operation of the fuel cell device of the presently filedembodiment during switch-over of antifreeze solution is described.

During switch-over of antifreeze solution, a situation wherein a flowpath 71 a and a flow path 71 b of the three-way valve 71 communicate oneanother and a flow path 73 a and a flow path 73 b of the three-way valve73 communicate one another is treated as an initial condition, and flowis proceeded in accordance with a flowchart of FIG. 12.

That is, first, operation is implemented to read in switch-over flags(FLG) “1” and “0” indicative of switch-over to be carried out andswitch-over not to be carried out, respectively (step 1201). Next,judgment is made to find switch-over FLG=1 (step 1203) and, ifswitch-over FLG=1, the flow paths 71 c, 71 b of the three-way valve 71communicate one another while the flow paths 73 a, 73 c of the three-wayvalve 73 communicate one another (step 1205). This allows air to beintroduced from the supply flow passage 75 to the hot medium flowpassage 25, with introduced air stream causing antifreeze solution to beexpelled from the hot medium flow passage 25 the antifreeze drain tank79 for air purging.

After a sufficient time period has elapsed for recovering antifreezesolution to the antifreeze drain tank 79, the respective flow paths 71b, 73 a and the respective flow paths 71 c, 73 c are closed to seal airintroduced into the hot medium flow passage 25 (step 1207). Thisantifreeze solution recovery time interval is appropriately determinedbased on experimental tests. If switch-over FLG≠1, the above-describedinitial states of the respective three-way valves 71, 73 are continued(step 1209).

This results in a capability of switching hot medium over fromantifreeze solution to air with no disposal of antifreeze solution and,thus, if antifreeze solution includes 50% ethylene glycol aqueoussolution, since a heat conductive rate is approximately 0.43 W/m/Kwhereas air has a heat conductive rate of approximately 0.024 W/m/K, aheat insulation property of the water tank 5 can be highly improved.

Also, in this case, as shown in FIG. 18 which will be described later,due to provision of a bypass flow passage 83 that allows the upstreamantifreeze circulation flow passage 3 of the three-way valve 71 and theantifreeze circulation flow passage 3 closer to the radiator 11downstream of the three-way valve 73, even if air is sealed in the hotmedium flow passage 25, it becomes possible to circulate antifreezesolution for cooling the fuel cell stack 1.

Further, while the presently filed embodiment has been described withreference to the water tank 5 that has the structure to which thestructure of the first embodiment is applied, the structure of the firstembodiment may also be applied to the water tanks 5 of the fourthembodiment shown in FIG. 7, the fifth embodiment shown in FIG. 8 and thesix embodiment shown in FIG. 10 such that the respective embodimentshave the following features.

In the first embodiment, due to the presence of the water tank 5 formedin the double-layer structure, a significant advantage results inavoiding water from frozen. Especially, when use is made in a districtwhere less frequency occurs in the ambient temperature dropping belowfreezing temperature, introducing air into the hot medium flow passage25 allows a priority to be particularly given for a merit of preventingwater from icing to permit water to be smoothly supplied during clodstart-up.

In the fourth embodiment, due to the existence of the structure whereinthe hot medium flow passage (composed of the annular conduits 47) ispiped in the inner wall of the water tank 5, the peripheries of theannular conduits 47 are surrounded by water, resulting in anadvantageous effect of efficiently achieving heat-exchange. That is, ina particular area, such as an extremely cold place (wherein noanti-freezing effect due to introduction of air is effectuated), wherefreezing frequently takes place, giving a top priority to thawingparticularly enables heat-exchange to be efficiently performed,resulting in smooth operation to supply water during cold start-up.

In the fifth and six embodiments, due to the presence of the structurewherein the hot medium flow passage (comprised of the annular conduits47 or the spiral shaped conduit 65) forms the side wall of the watertank 5, heat insulation effect is highly improved to enable efficientheat-exchange, thereby providing a compromise between block in freezingof water and efficient heat-exchange to some extent. If use is made inan intermediate district between an area to which the first embodimentis applied and another area to which the fourth embodiment is applied,the compromise between the effect of preventing water from being frozenand the effect in which efficient heat-exchange takes place is exhibitedto some extent, thereby enabling water to be smoothly supplied duringcold start-up.

FIG. 13 is a system structural view of a fuel cell device illustratingan eighth embodiment of the present invention. The presently filedembodiment contemplates to introduce combustion gas, expelled from thehydrogen combustor 19 through the heat exchanger 17, into the hot mediumflow passage 25 in place of air to be introduced to the hot medium flowpassage 25 of the fourth embodiment shown in FIG. 11 set forth above.Other structures are similar to those of the seventh embodiment.

That is, a three-way valve 87 is disposed in an exhaust gas exhaust flowpassage 85 connected to the heat exchanger 17, with the three-way valve87 and the three-way valve 71 disposed in the antifreeze circulationflow passage 3 disposed upstream of the water tank 5 being connected toone another by means of a combustion gas supply flow passage 89.

Now, operation of the fuel cell device of the presently filed embodimentduring switch-over of antifreeze solution is described.

During switch-over of antifreeze solution, a situation wherein a flowpath 87 a and a flow path 87 b of the three-way valve 87 communicate oneanother and the flow path 71 a and the flow path 71 b of the three-wayvalve 71 communicate one another while, further, the flow path 73 a andthe flow path 73 b of the three-way valve 73 communicate one another istreated as an initial condition, and flow is proceeded in accordancewith a flowchart of FIG. 14.

That is, first, operation is implemented to read in switch-over flags(FLG) “1” and “0” indicative of switch-over to be carried out andswitch-over not to be carried out, respectively (step 1401). Next,judgment is made to find whether switch-over FLG=1 (step 1403) and, ifswitch-over FLG=1, the flow paths 87 a, 87 c of the three-way valve 87communicate one another while the flow paths 71 c, 71 b of the three-wayvalve 71 communicate one another and, further, the flow paths 73 a, 73 cof the three-way valve 73 communicate one another (step 1405).

This allows combustion gas to be admitted to the hot medium flow passage25 through the combustion gas supply flow passage 89 to expel antifreezesolution from the hot medium flow passage 25 to the antifreeze draintank 79 for gas purging.

After a sufficient time period has elapsed for recovering antifreezesolution to the antifreeze drain tank 79, the respective flow paths 87a, 87 b communicates one another while the respective flow paths 71 b,73 a and the respective flow paths 71 c, 73 c are closed, respectively,to seal combustion gas introduced into the hot medium flow passage 25(step 1407). This antifreeze solution recovery time interval isappropriately determined based on experimental tests. If switch-overFLG≠1, the above-described initial states of the respective three-wayvalves 71, 73, 87 are continued (step 1409).

Consequently, with the presently filed embodiment, due to an ability ofhigh temperature combustion gas being introduced into and sealed in thehot medium flow passage 25, as the temperature of the sealed combustiongas drops, pressure reduction occurs in the hot medium flow passage 25,enabling the water tank 5 to have a highly improved heat insulationproperty.

FIG. 15 is a system structural view of a fuel cell device illustrating aninth embodiment of the present invention. The presently filedembodiment contemplates to incorporate an air tank 91, serving as an airstorage means, that stores combustion gas, into the combustion gas flowpassage 89 in the structure of the eighth embodiment shown in FIG. 13set forth above. Other structures are similar to those of the eighthembodiment.

When storing combustion gas in the air tank 91, the flow path 87 a andthe flow path 87 c of the three-way valve 87 communicate one another andthe flow path 71 c of the three-way valve 71 is closed. Under suchcondition, combustion gas generated in the hydrogen combustor 19 passesthrough the combustion gas exhaust passage 85 and the combustion gassupply flow passage 89 from the heat exchanger 17 and stored in the airtank 91.

During switch-over of antifreeze solution, a situation wherein the flowpath 87 a and the flow path 87 b of the three-way valve 87 communicateone another (with the flow path 87 c being closed) and the flow path 71a and the flow path 71 b of the three-way valve 71 communicate oneanother while, further, the flow path 73 a and the flow path 73 b of thethree-way valve 73 communicate one another is treated as an initialcondition, and flow is proceeded in accordance with a flowchart of FIG.16.

That is, first, operation is implemented to read in switch-over flags(FLG) “1” and “0” indicative of switch-over to be carried out andswitch-over not to be carried out, respectively (step 1601). Next,judgment is made to find whether switch-over FLG=1 (step 1603) and, ifswitch-over FLG=1, the flow paths 71 c, 71 b of the three-way valve 71communicate one another while the flow paths 73 a, 73 c of the three-wayvalve 73 communicate one another (step 1605).

This allows combustion gas in the air tank 91 to be introduced into thehot medium flow passage 25 through the combustion gas supply flowpassage 89 and the three-way valve 71 to expel antifreeze solution fromthe hot medium flow passage 25 to purge antifreeze solution into thedrain tank 79.

After a sufficient time period has elapsed for recovering antifreezesolution to the antifreeze drain tank 79, the respective flow paths 71b, 73 a and the respective flow paths 71 c, 73 c are closed to sealintroduced combustion gas in the hot medium flow passage 25 (step 1607).This antifreeze solution recovery time interval is appropriatelydetermined based on experimental tests. If switch-over FLG≠1, theabove-described initial states of the respective three-way valves 71,73, 87 are continued (step 1609).

Consequently, with the presently filed embodiment, even if the fuel cellelectric generation system remains in a halt condition, antifreezesolution in the hot medium flow passage 25 of the water tank 3 can bereplaced with combustion gas by using combustion gas stored in the airtank 91, enabling the water tank 5 to have a highly improved heatinsulation property.

Also, the structure in which the air tank 91 is provided can be appliedto the seventh embodiment of FIG. 11 set forth above. That is, in suchcase, the air tank 91 is disposed in the air supply flow passage 75shown in FIG. 11 and the three-way valve may be disposed in the supplyflow passage upstream of the air tank 91 for storing air in the air tank91.

FIG. 17 is related to a tenth embodiment of the present invention andshows a flowchart for setting the switch-over flag for use in antifreezeswitch-over in the seventh embodiment (FIGS. 11, 12), the eighthembodiment (FIGS. 13, 14) and the ninth embodiment (FIGS. 15, 16).

First, the antifreeze temperature T1 of the hot medium flow passage 25in the water tank 5 is measured by an antifreeze temperature gage 92serving as a temperature detection means (step 1701). Next, theantifreeze temperature T1 is compared with 0 C and αC (step 1703). Here,α designates a temperature with which reference is made for the heatcapacity of antifreeze solution to act on block of freezing of water inthe water tank 5.

Stated another way, since air has less coefficient of thermalconductivity than antifreeze solution, even at the same temperature of 0C, air is harder to be cooled than antifreeze solution and, so, there isa probability in which it is preferable for antifreeze solution to bereplaced with air at a timing with antifreeze solution remaining at ahigh temperature above 0 C to enable water to be avoided from beingfrozen in the water tank 5 as a whole. Thus, an upper limit of the hightemperature above 0 C is determined as αC.

In the above step 1703, if 0≦T1≦α, it is supposed for switch-over FLG=1(step 1705). If a situation does not stand for 0≦T1≦α, it is supposedfor switch-over FLG=0 (step 1707). Since α varies in dependence upon theatmospheric temperature and the heat dissipating condition of the watertank 5, it is possible to employ a method wherein this value may beclear from experimental tests for each condition as data base forcontrol in terms of parameters of the atmospheric temperature and theheat dissipating condition.

In response to this switch-over FLG, operation is executed to switchantifreeze solution, in the hot medium flow passage 25 in the water tank5, over to air as shown in the seventh, eighth and ninth embodiments.

Replacing antifreeze solution inside the hot medium flow passage 25 withair in such a way allows the heat capacity of antifreeze solution to beused to its maximum while preventing waste of an operating performanceof the fuel cell electric power generation system (to improve anefficiency), and combining this advantage with heat insulating action ofair enables water in the water tank 5 from being efficiently preventedfrom being frozen.

FIG. 18 is a system structural view of a fuel cell device illustratingan eleventh embodiment of the present invention. The presently filedembodiment contemplates to incorporate a bypass flow passage 83, in thestructure of the seventh embodiment shown in FIG. 11 set forth above,for bypassing the water tank 5. The bypass flow passage 83 has one endconnected to a three-way valve 93, that is disposed in the antifreezecirculation flow passage 3 upstream of the three-way valve 71, and theother end connected to the antifreeze circulation flow passage 3upstream of the radiator 11 and downstream of the heat exchanger bypassflow passage 15. Other structures are similar to those of the seventhembodiment.

In such case, an initial condition is set a situation where flow paths93 a, 93 c of the three-way valve 93 communicate one another, that is, asituation where antifreeze solution is admitted through the bypass flowpassage 83, and operations are executed in accordance with a flowchartof FIG. 19.

That is, first, the water (or ice) temperature T3 of the water tank 5 ismeasured by the temperature gage 41 (step 1901).

Next, resulting detected temperature T3 is compared with the bypassjudgment temperature T30 (step 1903) and, if T3>T30, judgment is madethat there is no need for heating the water tank S on the suppositionthat the water temperature of the water tank 5 exceeds a prescribedvalue whereupon the flow paths 93 a, 93 c continues to communicate oneanother while antifreeze solution is passed to the bypass flow passage83 so as to bypass the water tank 5 (step 1905).

Meanwhile, if no situation stand for T3≧T30, judgment is made that thereis a need for heating the water tank 5 on the supposition that the watertemperature of the water tank 5 is below the preset value, and the flowpaths 93 a, 93 b of the three-way valve 93 communicate one another toallow antifreeze solution to be supplied to the hot medium flow supplypassage 25 of the water tank 5.

Consequently, with the presently filed embodiment, if there is no needfor heating water in the water tank 5, since no antifreeze solution isrequired to flow through the hot medium flow passage 25, a pressure lossin the flow passage due to flow of antifreeze solution can be minimizedand a load of an antifreeze pump, which is not shown, can be decreased,resulting in improvement in an efficiency of a whole system.

FIG. 20 is a cross sectional view of a water tank 5F for use in a fuelcell device of a twelfth embodiment of the present invention. The watertank 5F of the presently filed embodiment takes the form of adouble-layer structure, comprised of the inside tank component 21 andthe outside tank component 23, like the one of the first embodimentshown in FIGS. 1 to 3, between which the hot medium flow passage 25 isdefined to allow antifreeze solution to flow.

The hot medium flow passage 25 accommodates therein a heat insulationmember 95 which is shown in a perspective view in FIG. 22. The heatinsulation member 95 has a center formed with a through-bore 95 a, sothat it is accommodated in a space (hot medium flow passage 25) betweena peripheral side wall of the inside tank component 21 and a peripheralside wall of the outside tank component 23, and is formed of materialwith a specific gravity greater than that of air but less than that ofantifreeze solution to be moveable in the vertical direction.

For this reason, in FIG. 20, the heat insulation member 95 is floatingupward in antifreeze solution and, in FIG. 21, the heating insulationmember 95 in air is located downward in the hot medium flow passage 25.

A stopper member 97 is mounted in the inside tank component 21 tosupport the heat insulation member 95 during downward movement of theheat insulation member 95. Outer peripheral sides of the stopper member97 are positioned apart from opposing inner peripheral walls of theoutside tank component 23, thereby allowing antifreeze solution or airto flow out of the antifreeze solution outlet 29. The heat insulationmember 95 is made of material such as styrol foam and evacuated heatinsulation material with core material composed of silica powder.

As shown in FIG. 20, if antifreeze solution is introduced into the hotmedium flow passage 25, the heat insulation member 95 moves upward(floats) and prevents heat from escaping to the space (an upper areaabove a water level L) in the inside tank component 21, therebypromoting thawing or heating.

Meanwhile, if air is introduced into the hot medium flow passage 25 asshown in FIG. 21, the heat insulation member 95 moves downward todecrease the degree of heat dissipation from water, thereby improving aheat dissipating effect.

Consequently, according to the presently filed embodiment, it ispossible to improve a thawing property, a heating property and a heatinsulation property.

FIGS. 23 and 24 are cross sectional views of a water tank 5G for use ina fuel cell device of a thirteenth embodiment of the present invention.The water tank 5G of the presently filed embodiment takes the form of adouble-layer structure, comprised of the inside tank component 21 andthe outside tank component 23, like the one of the first embodimentshown in FIGS. 1 to 3, between which the hot medium flow passage 25 isdefined to allow antifreeze solution to flow.

In place of the heat insulation member 95 of the twelfth embodimentshown in FIG. 22 set forth above, a plurality of spherical heatinsulation members 99, that form a plurality of members smaller than theflow sectional area of the hot medium flow passage 25 between the insidetank component 21 and the outside tank component 23, are accommodated inthe hot medium flow passage 25.

These heat insulation members 99 are formed of material with a specificgravity greater than that of air but less than that of antifreezesolution like the heat insulation member 95 of FIG. 22 set forth above.Accordingly, when antifreeze solution is introduced in the hot mediumflow passage 25, the heat insulation members 99 take a state whereinthey are floating upward as shown in FIG. 23 and, when air is introducedin the hot medium flow passage 25, the heat insulation members 99 take asinking state as shown in FIG. 24. To prevent the heat insulationmembers 99 from escaping from the antifreeze solution outlet 29 in sucha case, the inside tank component 21 is provided at its lower portionwith a heat-insulation member escape block member 101. Theheat-insulation member escape block member 101 may be comprised of anet-like configuration.

Accordingly, the heat insulation members 99 of the presently filedembodiment are able to move upward when antifreeze solution isintroduced and to move downward when air is introduced even in a casewhere the spiral shaped antifreeze rectification plate 45 as in theembodiment shown in FIG. 5 set forth above, thereby enabling acompromise between an improved heat exchange efficiency of theantifreeze rectification plate 45 and a thawing property, humidifyingproperty and a heat insulation improvement of the heat insulationmembers 99.

INDUSTRIAL APPLICABILITY

As set forth above, according to the present invention, due to anability of antifreeze solution, heated by the antifreeze heating means,permitted to flow through the hot medium flow passage located in thewater storage means, even if water stored in the water storage means isfrozen, frozen water can be rapidly thawed by heated antifreeze solutionin an efficient manner.

The entire content of Japanese Application No. P2002-246873 with afiling date of Aug. 27, 2002 is herein incorporated by reference.

Although the present disclosure has been described above by reference tocertain embodiments of the invention, the invention is not limited tothe embodiments described above and modifications will occur to thoseskilled in the art, in light of the teachings. The scope of theinvention is defined with reference to the following claims.

1. A fuel cell device comprising: a fuel cell cooled by antifreezesolution; an antifreeze circulation flow passage to allow the antifreezesolution to be circulated; an antifreeze heater disposed in a midway ofthe antifreeze circulation flow passage to heat the antifreeze solution;a water storage unit that stores water to be supplied to the fuel cell;and a hot medium flow passage disposed in a water contact section of thewater storage unit to allow the antifreeze solution, heated by theantifreeze heater, to flow.
 2. The fuel cell device according to claim1, further comprising: a water pump drawing water, stored in the waterstorage unit, to an outside; and a suction conduit heater sectiondisposed around a periphery of a water suction conduit of the water pumpto allow the heated antifreeze solution to flow.
 3. The fuel cell deviceaccording to claim 1, further comprising: an antifreeze rectificationplate disposed in the hot medium flow passage to rectify flow of theantifreeze solution.
 4. The fuel cell device according to claim 1,wherein the hot medium flow passage is disposed along at least a portionan inner wall of the water storage unit.
 5. The fuel cell deviceaccording to claim 1, wherein the hot medium flow passage is formed in aplurality of stacks to allow mutually adjacent, stacked hot medium flowpassage components to be sealed watertight, and the stacked hot mediumflow passage components form at least a portion of a side wall of thewater storage unit.
 6. The fuel cell device according to claim 4,wherein the hot medium flow passage is formed in a spiral shape.
 7. Thefuel cell device according to claim 1, wherein the hot medium flowpassage has an antifreeze solution inlet, through which the antifreezesolution flows in, located at a higher position than an antifreezesolution outlet, through which the antifreeze solution flows out.
 8. Thefuel cell device according to claim 1, further comprising: a switch-overunit expelling the antifreeze solution from the hot medium flow passageto allow air to be admitted to the hot medium flow passage in place ofthe expelled antifreeze solution.
 9. The fuel cell device according toclaim 8, further comprising: an antifreeze accommodating unit that, whenthe hot medium flow passage is admitted with air in place of theantifreeze solution, allows the air to expel the antifreeze solutionsuch that the expelled antifreeze solution is accommodated.
 10. The fuelcell device according to claim 8, wherein the air to be admitted to thehot medium flow passage in place of the antifreeze solution includescombustion gas resulting from a combustor disposed in the antifreezeheater.
 11. The fuel cell device according to claim 8, furthercomprising: an air storage unit storing air to be introduced into thehot medium flow passage in place of the antifreeze solution.
 12. Thefuel cell device according to claim 8, further comprising: an antifreezetemperature detector detecting the temperature of the antifreezesolution in the hot medium flow passage; wherein when the temperature ofthe antifreeze solution is detected to fall in a value higher than 0 Cand lower than αC (α: heat capacity reference temperature of theantifreeze solution), the antifreeze temperature detector controls thehot medium change-over unit so as to allow the air to be admitted to thehot medium flow passage in place of the antifreeze solution.
 13. Thefuel cell device according to claim 1, further comprising: a watertemperature detector detecting a water temperature in the water storageunit; and a bypass unit bypassing the hot medium flow passage; whereinwhen the detected water temperature exceeds a preset value, the watertemperature detector controls the bypass unit to allow the antifreezesolution to bypass the hot medium flow passage.
 14. The fuel cell deviceaccording to claim 8, wherein the water storage unit includes adouble-layer structure composed of an inside tank component and anoutside tank component, between which the hot medium flow passage isformed, and a heat insulation member with a specific gravity greaterthan the air and less than the antifreeze solution is moveably receivedin the hot medium flow passage.
 15. The fuel cell device according toclaim 14, wherein the heating member includes a plurality of memberssmaller in size than a flow sectional area of the hot medium flowpassage formed between the inside tank component and the outside tankcomponent.
 16. The fuel cell device according to claim 1, wherein theantifreeze solution heated by the antifreeze heater heats the fuel celland heat the water in the water storage unit while flowing through thehot medium flow passage.
 17. A fuel cell device comprising: a fuel cellcooled by antifreeze solution; antifreeze circulation means forcirculating the antifreeze solution; antifreeze heating means forheating the antifreeze solution flowing through the antifreezecirculation means; water storing means for storing water to be suppliedto the fuel cell; and hot medium flow passage means disposed in a watercontact section of the water storing means to allow the antifreezesolution, heated by the antifreeze heating means, to flow.
 18. A methodof controlling a fuel cell device, the method comprising: preparing afuel cell; preparing a water storage unit, to store water to be suppliedto the fuel cell, that has a hot medium flow passage; circulatingantifreeze solution to the fuel cell and the hot medium flow passagethrough an antifreeze circulation flow passage; and heating theantifreeze solution flowing through the antifreeze circulation flowpassage for thereby heating the water in the water storage unit.